Field of the Invention
The present invention relates generally to the field of vibration testing of objects such as satellites, instrumentation or any other object whose reliability in operation may be evaluated using high intensity vibration testing. Specifically, the present invention relates to the use of direct field acoustic systems to perform vibration testing and to control means to allow direct field acoustic systems to produce a an acoustic field conforming to a predetermined specification.
Background of the Invention
The specification of co-pending U.S. application Ser. No. 13/117,870, filed May 27, 2011 titled Direct Field Acoustic Testing System and Method (hereinafter “the '870 application”) is incorporated by reference herein. As discussed in the '870 application, in the field of Direct Field Acoustic Testing (DFAT) it is generally desirable to obtain an acoustic field having a uniform spectral content throughout the space around the Unit Under Test (UUT). As demonstrated in the '870 application excellent spectral uniformity was obtained at the control microphone locations through the use of a Multiple-Input-Multiple-Output (MIMO) arrangement incorporating multiple groups of independently controllable acoustic transducers. However, monitoring of the acoustic field with additional non-control or monitoring microphones has shown that while spectral variations are well controlled at the control locations, greater variations and deviations from specification exist at non-control locations. A general shift to higher acoustic intensities at the non-control locations has also been observed for frequencies generally above 150 Hz leading to a risk of over testing the UUT. It is therefore advantageous to provide an enhanced DFAT system which reduces these variations and maintains a closer correspondence between the spectral acoustic magnitude response at control and non-control locations.